Apparatus for spraying metals



Oct. Z7, 1936. H. R. FoRTON APPARATUS FOR SPRAYING METALS Filed Dec. 19, 1955 ik Wm n f .ILV Q OJ M w, Gm A.di \\\\\\\\\\\\\\w\\\\ E .s Y B uw EL mw w A a l VIA lll/ll "rammed oei. 27, 1936 UNiTEo STATES APNPENT,oluucrj ,APPARATUS Fon srnarmc METALS Harold B. Fortan, Detroit, Mich.- applicati@ ummm-.19, ,1935, serai Na 55,113

's claims. (c1. sz-sii This invention relates to apparatusfor atomizing `and-spraying molten metal, and aims to provide in very compact and readily portable hand or gun" form, metal spraying equipment' of especially convenientY 'and reliable character. An aim of particular importance in developing the present invention has been the provision, in a device of the character indicated, of electrical heating means, means for automatically v '20 is delivered,.melted and discharged continuously at the same rate, and projected practically immediately upon melting rather than stored in the instrument, 'as a result of which oxidation,

' and the clogging at the nozzle which it causes in 25 many types of metal spraying equipment, are

prevented.

Another object is a device of the sort indicate in which the nozzle may be cleaned quickly and easily, without removing it from the apparatus, '30 and in which the conveying tube Vfor the metal,

together with the nozzle, may at any time and whether hot or cold be instantly removed and replaced. Another object comprises the provision of such 35 a spraying device incorporating air blast means for discharging molten metal, together with electric metal heating means, and provided with automatic switching means responsive to the turning on and oil the air blast for reducing the o wattage when the air is turned on, in a fashion which automatically maintains themetal-melting portionsat uniform temperatures regardless of the presence or absence of the air blast and its cooling effect, the arrangement -being such 45 that the vair blast when operating prevents the heating elementfrom burning 'out although the element is operated above the capacity at which `it could be rated to' operatewithoutfarticial cooling. A related object is the provision in 50 conjunction with the. means last mentioned of automatic operating means for starting and stopping the metal feeding apparatus when the air blast is turned on and off.

Other objects and advantages will be apparent l55 from the following description, wherein reference is made to the accompanying drawing illustrating a preferred embodiment of myinvention, and wherein similar reference numerals designate similar parts throughout lthe several views.

' In the drawing:

'I'he singielflgure is a partly diagrammatic view showing in longitudinal section the spraying device and the control box containing the automatic regulating apparatus, showing schemati- .10 cally the connections between these elements and the operating motor for the metal feed.

Referring now to the drawing, reference character I0 represents a casing, the front or bottom. face of which is substantially but not entirely closed, and centrally apertured as at I4 t'o provide an air jet opening which is also partly defined by the spacedly intertted nozzle I5 through which the metal is discharged, the metal being drawn therethrough and aspirated by the air blast. An air delivery chamber I8 surrounding the nozzle and jet opening is formed in the front wall portion by which plate I2 is carried, such plate closing the front of the chamber. The air may be conducted to the chamber for discharge through the air jet opening by an air" tube 22, which may pass through the hollow handle 25.

'I'he wall 20 is secured to the casing by screws 26 but spaced therefrom to provide a passage 21 through which air may enter the casing from beneath. A vent 28 is also preferably provided in the' back wall of the casing, the vent being 'shown guarded by a hat 29 pivoted to the back wall in such lfashion that it may be swung free of the vent.

The metal to be melted, designated 30, may

also be fed through the hollow handle, in wire form, a conveyor tube as 32 being provided therefor arranged to discharge it directly into the open upper end of the Crucible 33. The metal is advanced by friction feeding rolls as 35, driven by worm or'o'ther suitable gearing 3 1 turned by a flexible shaft 38, which may also extend from the end of the hollow handle to a driving motor 40, which may be carried upon a work bench (not shown) or other suitable xed support.

The crucible is not intended at any time to hold a. reserve supply of metal, the parts being so proportioned that the metal merely passes therethrough, being melted and discharged as rapidly as delivered. The discharge nozzle I5, formed lintegrally with the Crucible, communic'ates directly with the interior thereof, a frustoconical or equivalently shaped bottom being "pro- .55

air Jet communicates with an annular opening 3l formed in the bottom of the crucible and partly overlying the wall 20. The crucible rests loosely in place, as does also the electrical heating unit assembly surrounding the same and generally designated 40. A small quantity of heated air may accordingly leak beneathv the crucible and heating element andinto the chamber 35, whence it may pass out through the air blast nome, traveling in direct contact with the metal discharge nozzle i5 and forming thereabout a.

skin or thin layer of highly heated air which prevents undue cooling of the metal in the nozzle by the air blast.

The conveyor tube l2, although shown as blockin g removal of the crucible from the rear when in operative position,'is preferably so held in place that it may be slid back into the handle and out ofthe way, being releasably supported in a bracket 4I and held by a set screw 42. When the tube is slid back the crucible may be quickly removed and replaced; The heating element is shown as a tapped coiled resistance wire 45 held between refractory sleeves 48-48, although it might of course be wound and supported in any other suitable'fashion. The crucible nts slidably' within the inner coil form.

By reason of the intermediate tap (connected towire 12b) the heating element is divided into upper and lower sections, designated 45a and lib. These are so proportioned that when operated in series they are capable of holding the crucible at the proper temperature for melting the metal when the air blast is not in operation, while when only the section 6b is in operation, and the entire-current is passedtherethrough, the wattage being of course greatly increased, the greater rate of heat delivery is such that the desired temperature of the crucible may be maintained with the air blast in operation.

A main valve 50 is provided in the air line, and the current supply for the motor and heating element is indicated as controlled by a hand switch 5I.

Automatic switching means is also provided for so lcontrolling the heating element operation as toincrease its wattage when the air blast is4 turned on, by shorting out the upper section a, and decrease the wattage by opening the short-circuit to place both sections (45m-45h) in series when the air blast is shut off. Such switching means' includes a Pressure cylinder 5B, connected to the air supply line between the main valve 50 and the nozzle, as bymeans of air hose 58, a piston U reciprocable in the cylinder and operable by the back pressure from the air nozzle to throw switch blades Gil-6I into shunting relation with respect to contacts 62-83 and 64-65. The switch blades are carried by an insulating disc Il mounted upon the end of piston rod B9 which extends from cylinder 55. The air cylinder and switching means areY shown mounted in a single casing 1l which is intended to be carried upon the bench or wall in fixed position and connected to the spray gun by flexible conduits 56, 12, the latter carrying the wires, designated 12a-12b and 12e, for the heatingl element. When the air pressure is s hut of! the piston is `returned and the shunt circuits opened by a spring ll trapped and acting upon the piston rod. Power leads "-13, connected to contacts l5-82, respectively are also directly connected to the ends of heating coil II, so that when the shunt switches are open and the current on, the entire coil is energized. One'termlnal of the motor Il is connected to contact 8l, the motor being thus energized only when contacts 82-63 are bridged by switch blade 80. Contact ll is connected to wire 11b which runs -to the center tap of the heating element.

vIt will be .seen that when switch blade il connects contacts M wires 12b- 12e are bridged and the upper section 45a of the heating element short-circuited, the motor lll being simultaneously energized, since the switches Bil-6| operate together.

Although the operation will doubtless be clear from the foregoing, it may be briefly summarized .as follows: If desired, switch 5i may remain closed and the current be supplied continuously, in which event the crucible remains hot and ready for instant operation, even thoughv valve 50 be closed. Under such conditions switch blades GII-6I occupy the positions in which they are shown in the drawing, the shunt circuits between.

contacts 62-83 and 84-65 remaining open, the motor deenersized and current flowing through the entire heating coil. When it is desired to operate the gun, the valve 50 is opened, which immediately applies pressure to the piston, closing switches 80--8I shorting out heating coil section 45a and imposing the entire current upon section lib, the temperature and heat delivery of which is -immediately greatly raised. The motor lilbeing simultaneously started, metal is immediately delivered to the cruclble, whence it is forced through the nozzle by atmospheric'pressure, due to the reduction of pressure created at the mouth of the nozzle by the air blast, which also aspirates and projects the molten discharge. Heating coil section 5b is so proportioned that it would burn out but for the cooling influence of the air blast. For this reason it has the property of lagging but a very short time in reaching the increased temperature when section lla is shorted out, and as quickly-drops to the lower temperature when section 45a is again placed in circuit.

What I claim is:

1. In a'device of the character described, in combination with means for supplying air under having an air jet opening therein, metal convey- 'ing and heating means within the casing including an electrical heating element surrounding a portion of the conveying means, and a nozzle portion for molten metal connected to the conveying means and having a discharge opening adjacent the air jet opening, means including an electric switch for changing the eifective'heat delivery of the heating element, and means responsive to a change of pressure in the air supply means for operating said switch.

2. In a device as set forth in claim 1, electrically `operable means for feeding metal to the conveying means, switching means for controlling the operation of said electrically operable feeding means, and means for operating said last mentioned switching means also in response to change of pressure in the air supply means.

3. In combination with means for supplying vair under pressure, and a source of electric current, metal spraying means including a casing having an air jet opening therein connected to the air supply, a metal melting receptacle within the casing, said casing also having a nozzle portion adjacent the air jet opening and connected to the metal melting receptacle for discharging molten metal, an electric heating element arranged to act upon said receptacle, means for changing the eiective heat output of said heating element including an electric switch, valve means for starting and stopping the air supply, and means responsive to starting and stopping of the air supply for operating said switch to increase the heat output when the air supply is turned on, and to decrease the heat output when the air supply is turned off, the means for changing the heat output and the heating element being so proportioned to the air supply as to maintain the temperature of thev metal melting receptacle substantially constant by virtue of such changes of heat output of the heating element.

4. Apparatus as set forth in claim 3 including electrically operable metal feeding means for supplying metal to said receptacle, and means for starting the metal feeding means when the air supply is turned on, and for stopping said feeding means when the air supply is turned oif.

5. Apparatus as set forth in claim 3 including pressure-responsive means for throwing said switch connected to the air supply means between the valve and the air jet.

6. Apparatus as set forth in claim 3 including electrically operable metal feeding means for supplying metal to said receptacle, and means including a second switch for starting the metal feeding means when the air supply is turned on, and for stopping said feeding means whenV the air supply is turned off, and common pressureresponsive operating means for both of said switches connected to said air supply means.

HAROLD R. FORTON. 

